1. Field of the Invention
This invention generally relates to the manufacture of a wound ball, typically a wound golf ball comprising a core having rubber thread wound on a spherical center and a cover on the core. More particularly it relates to a method and apparatus for winding rubber thread on the center to form the wound core.
2. Prior Art
In general, wound golf balls are manufactured by winding rubber thread around a center, which is either a liquid center in the form of a rubber bag filled with a liquid or paste or a solid center made of solid rubber, to form a wound core, and enclosing the core with a cover.
It is a common practice to wind rubber thread on a center by holding the center among a plurality of rotatable winding rollers, feeding rubber thread to the surface of the center, and driving at least one of the winding rollers for rotation for thereby winding the rubber thread around the center. When rubber thread is to be wound on the center by this method, a leading end of rubber thread must be secured to the center at the start of winding. The following various techniques are known and used for securing the leading end to the center.
(1) Rubber thread is wound two or three turns on a center such that the leading end is interposed between the center surface and the turns of rubber thread, thereby fastening the leading end to the center.
(2) The leading end of rubber thread is placed on the surface of a center and adhesive is applied thereat to adhesively bond the leading end to the center surface. See Japanese Patent Publication (JP-B) No. 49985/1986.
(3) In the case of a liquid center, it is frozen before rubber thread is wound thereon. The leading end of rubber thread is placed on the surface of the frozen liquid center, and water is applied thereat. Then water is cooled and solidified whereby the leading end is tacked to the center surface. See Japanese Patent Application Kokai (JP-A) No. 126470/1976.
These leading end securing techniques, however, have the following problems. Technique (1) of binding rubber thread to the center is currently carried out by manual operation because of difficulty of automation. The manual binding operation is cumbersome and requires skill, contributing to a reduction of efficiency in the manufacture of wound golf balls.
The adhesive technique (2) has problems in that (i) after a droplet of the adhesive is applied, it is dried and cured over a certain time, (ii) due to tackiness of the adhesive, foreign matter is likely to adhere thereto, (iii) the winding apparatus is contaminated with the adhesive and its maintenance becomes cumbersome, (iv) the adhesive is not applicable to a liquid center because the liquid center is frozen before winding of rubber thread and the adhesive does not perform on the frozen center, and (v) the adhesive is eventually left in the ball to alter its performance.
The tacking technique (3) based on freezing of water has the problems that (i) solidification of water takes some time, (ii) water causes rust and dew in the winding apparatus, (iii) water adversely affects the winding apparatus, and (iv) application is limited to only liquid centers.
The prior art winding methods are not fully satisfactory with respect to efficient manufacture and quality reliability of products because many problems arise in securing the leading end of rubber thread to the center. There is a desire to have a winding method which can solve the problems associated with the start of rubber thread winding and produce wound golf balls of quality in an efficient manner.